Question

What is the resistance of \(\mathrm{P}-\mathrm{N}\) junction diode in forward biasing ? (A) zero (B) high (C) infinity (D) a few ohms

Short answer

The resistance of a PN junction diode in forward biasing is a few ohms (D).

Step-by-step solution

Understanding PN Junction Diode

A PN junction diode is formed by joining a P-type semiconductor material (having an excess of holes) with an N-type material (having an excess of electrons). The P-side is connected to a positive terminal, and the N-side is connected to a negative terminal. When the diode is forward biased, the voltage is applied in such a way that it decreases the barrier potential, allowing current to flow through the diode.

Diode Behavior in Forward Biasing

In the forward biasing condition, the electric field created by the battery works against the internal electric field of the PN junction diode, narrowing the depletion layer. This reduction in the depletion layer allows the majority charge carriers (holes and electrons) to pass through the junction relatively easily. This enables an electric current to flow through the circuit.

Analyzing the Resistance Options

In forward biasing, the diode allows the flow of current, thus, the resistance is not infinity. However, as it does not offer a completely unobstructed path, the resistance cannot be zero. Furthermore, the forward-biased diode provides relatively low resistance as it allows the current to flow easily. Now, let's analyze the given answer choices based on these observations. (A) zero - Not possible because it offers some resistance when the current flows through it. (B) high - Incorrect as the resistance in forward-biased diodes is not high. (C) infinity - Not possible, as in this case, no current would flow through it in forward biasing. (D) a few ohms - Appears to be the correct choice, as the forward-biased diode provides a relatively low resistance path for the current.

Conclusion

The resistance of a PN junction diode in forward biasing is a few ohms (D).